In recent years, in order to enhance the operation sense of the driver and create driving amenity inside a vehicle, such as an automobile, mainly automobile manufacturers have been proposing various techniques. A known technique among these proposals is to output a simulated engine sound from the sound output part incorporated in the vehicle in response to the driving status of the vehicle.
FIG. 11 is a block diagram of conventional sound output device 501 disclosed in Patent Literature 1. Sound output device 501 includes driving-status detector 101, sound signal generator 102, sound level adjusters 104A and 104B, and speakers 105A and 105B connected to sound level adjusters 104A and 104B, respectively. In response to the driving status of the vehicle detected by driving-status detector 101, sound signal generator 102 generates a simulated engine sound. The generated simulated engine sound is adjusted by sound level adjusters 104A and 104B, and output from speakers 105A and 105B.
By outputting the simulated engine sound, sound output device 501 emphasizes, to the driver of vehicle 106, the sound with which the number of rotations of the engine is changed by the operation of the accelerator, and enhances the operation sense of the driver of vehicle 106. Further, by mixing the simulated engine sound with an original engine sound, sound output device 501 creates an engine sound having comfortable frequency characteristics for the driver and improves the driving amenity of the driver.
In FIG. 11, components, such as driving-status detector 101, of sound output device 501, are shown outside vehicle 106. However, actually, these components are installed inside vehicle 106 similarly to speakers 105A and 105B.
In conventional sound output device 501, the simulated engine sound output from speakers 105A and 105B interferes with the sound reflected on an inside, such as wall surfaces, of vehicle 106, and produces a peak or a dip at a specific frequency of the output sound. As a result, passengers sitting at predetermined positions, such as a driver seat and a front passenger seat, may not hear a desirable simulated engine sound.